Method of producing an ignescent material

ABSTRACT

PCT No. PCT/SE84/00398 Sec. 371 Date Jul. 14, 1986 Sec. 102(e) Date Jul. 14, 1986 PCT Filed Nov. 20, 1984 PCT Pub. No. WO86/03219 PCT Pub. Date Jun. 5, 1986.The manufacturing of an ignescent material comprises feeding cellulose pulp in the form of a web (6) through a bath (2) of molten, combustible, organic impregnating substance, said substance being solid at room temperature, thereby soaking said pulp with said substance. According to the invention, more than 50% of the pulp is chemically modified thermomechanical pulp, so called CTMP. The impregnating substance is preferably paraffin.

TECHNICAL SCOPE

The present invention relates to a method of producing an ignescentmaterial, said method comprising the feeding of cellulose pulp in theform of an elongate web through a bath of molten, combustible, organicimpregnating substance, said substance at room temperature being solid,thereby soaking said pulp with said substance.

BACKGROUND ART

For the ignition of briquets and charcoal for grills up till nowignescent fluid has been the dominating and sole accepted ignition aidfor producing in an acceptably short time embers for broiling. Among thedrawbacks of ignescent fluid are the hazards of the ignition procedure.At times, ignescent fluid has been confused with other fluids and causedsevere burns in children and in some known instances children have beenpoisoned by drinking the fluid. In addition, the ignescent fluid isbulky and generally difficult to bring along. It sometimes also impartsobtrusive flavours to the food being broiled. The use of ignescent fluidis also expensive.

To light a fire in fireplaces, furnaces, and suchlike, one normally usesnewspaper leaves and the like, in conjunction with wood chips. This is atime-consuming method. Ignition aids known as `fire lighters` may alsobe used. A method for producing fire lighting aids was described inSE-A-No. 41 897, in 1914. According to this method, paper, sulphite orsulphate pulp, is impregnated with a combustible substance which iseither liquid or solid, such as resin, resin dissolved in somecombustible substance such as spirits, turpentine, raw or refinedpetroleum, tar, or some other suitable substance. After beingimpregnated, the paper or the pulp is rolled onto spindles, and firelighting aids then prepared from the strips, whether wet or dry, thefinal product being in the form of small reels. According to SE-A-No. 96174 fire lighters are produced from lumbering or wood mill debris, whichis cut into chips, defibrated, mixed with water to achieve a suitableconsistency and lastly formed into a plate, which is dewatered bypressing and then dried. This plate is dipped in molten paraffin,stearin, or tallow or a mixture of these at a temperature of 80°-100° C.After drying, the plate is cut into pieces of a certain width andlength. Before being impregnated, the plate is provided with grooves, tofacilitate the cutting of the plate into small square blocks.

A drawback which is common to these and other known fire lighting aidsis that the area of combustion is small, the product thus having to beignited at a very small area. Therefore, it is not at all uncommon tofail at the ignition of these products, even if the burning time may belong. In addition, the positioning of the lighter is critical, forinstance when lighting a fire on a grill, since the lighter, being verysmall, may easily fall down through the grid.

Another known lighting aid consists of cubes of a brittle material whicheasily crumbles and has a strong odour, so that the product must becarefully packed and gently handled.

Paraffin impregnated cellulose pulp is a better lighting aid. The areaof combustion of this product in relation to its volume is greater, andhence the product burns more intensely and over a larger area. Eventhough its burning time is shorter than that of a more compact productof the same volume, the fire or the bed of briquettes or coal to beignited is lit more effectively and more safely. Another desirableproperty of the lighter is that it is free of tackiness. Nor should itcrumble when broken, as is the case if not all paraffin has becomeabsorbed into the pulp. At the same time it must be water-repellent andinflammable. These demands have caused considerable manufacturingproblems.

DISCLOSURE OF INVENTION

The object of the invention is to solve the manufacturing problemsmentioned. Particularly, an object of the invention is to provide amethod of producing lighting aids by impregnating cellulose pulp with acombustible substance so that a non-tacky, sheet-formed product results.This object may be realized by letting more than 50%, preferably morethan 75%, of the cellulose pulp be chemically modified thermo-mechanicalpulp, CTMP. The rest of the material may be, eg sulphate pulp. Theimpregnating substance is preferably paraffin with a melting point ofbetween 50° and 60° C., the impregnating melt then being held at above90° C., preferably above 100° C., although not above 130° C., preferablynot above 115° C. At these temperatures, impregnation is quick andexcess impregnating substance is drained off in a short time, so that noexcess substance stays on the surface, there to solidify. At highertemperatures, the pulp softens too much, in other words it looses itsmechanical strength to such a degree that it may not be fed continuouslythrough the melt without risk. In other words, the web may break. Underthe conditions stated, the pulp, being fed continuously through themelt, need not be submerged in the melt for more than 5 to 20 seconds.Preferably, it should not be submerged for more than 15 seconds.

When the cellulosic material is fully saturated with the impregnatingsubstance, as evidenced by the cessation of bubbles escaping from thepulp, the excess substance is allowed to drain, and then the impregnatedmaterial is cooled while flat until the temperature reaches 20° to 40°C., preferably to a temperature between 25° and 35° C. At thistemperature, the paraffin solidifies quickly in the pulp. A lower or ahigher temperature leads to difficulties when the product is cut intoflat sheets, which are then piled and strapped. At lower temperatures,the strapping paper or the label does not stick to the product, andfurthermore, the sheets tend to bend. At higher temperatures, problemsarise in connection with the cutting into sheets, the material tendingto be sticky and the edges fringing.

Further characteristics, aspects, and advantages of the invention willbecome apparent from the appended patent claims and the followingdescription of experiments done and of a preferred embodiment.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of the manufacturing method and ofexperiments carried out, reference will be made to the attached drawingswherein

FIG. 1 schematically illustrates the manufacturing process and theequipment used therein, and

FIG. 2 shows a package with a number of sheets of the lighting aidaccording to the invention.

DESCRIPTION OF MANUFACTURING TECHNIQUE AND EXPERIMENTS DONE

The technique applied and the equipment utilized in the manufacturingprocess are illustrated in FIG. 1. The starting materials are a roll 1of cellulose pulp and molten paraffin 2 in a trough 3. The melt isproduced in a melting-pot 4. An exhaust hood is designated 5. Theparaffin is of foodstuff quality. Its melting point is between 52° and58° C., it is essentially free of aromatic substances, and has an oilcontent of less than 1%, preferably less than 0.5%. The pulp is reeledoff the roll 1 continuously and the web 6 is fed through the melt 2 bymeans of two pairs 7, 8 of feeding rollers. The web 6 is dragged alongthe bottom of the trough 3 at a speed which allows the soaking of theweb material 6 to be completed just before the web is pulled out of themelt 2. The infiltration of molten paraffin into the pulp is indicatedby small bubbles rising to the surface of the melt, while the web 6passes through it. The cessation of this formation of bubbles isevidence that the pulp is saturated with paraffin, and the web feedingspeed should be set accordingly.

The web material 6 thus having become saturated with paraffin in themelt 2, excess paraffin is allowed to drain as the web passes through ashort draining zone 10, before entering a cooling chamber 11, in whichit is cooled by air until it reaches a temperature slightly aboveambient. In the cooling chamber 11, the soaked web is dragged along thebottom of the cooling trough by means of the feeding rolles 7, so thatthe web is extended and becomes flat before the paraffin solidifies inthe pulp. As the web leaves the chamber 11 the temperature has beenlowered to between 25° and 35° C. The next step in the productionprocess is to cut the stiff web material 6' into pieces 10 cm long, in acutter 12. Finally the finished lighting aids 13, in the form of sheets,2 mm thick and 10×20 cm wide and long, are fed to a piling and strappingmachine 14, which straps a gummed label 15 around them, see FIG. 2. Thepile of sheets has been designated 16.

EXPERIMENTS

For the following experiments foodstuff quality paraffin was used. Thedifferent examples serve to show the importance of the choice ofcellulosic material.

EXAMPLE 1

In this case sulphite pulp was used. Several problems were noted. Thelighting aid obtained was of a highly varying quality, because theparaffin did not penetrate the material evenly. Nor did the paraffindrain easily in the draining zone. The surface did not become dry andfibrous, as desired. Instead, it became fatty, slippery, and smeary, andparaffin which had solidified on the surface crumbled. In addition, theweb had to be forwarded slowly through the melt, so as to achieve atleast some degree of saturation.

EXAMPLE 2

In this case the web material was board as used for egg cartons. Theresult was as negative as for the sulphite pulp of example 1. Theimpregnation required a dwell time of 60 seconds for a melt temperatureof 100° C.

EXAMPLE 3

The following saturation times were noted with purely mechanical pulp.

    ______________________________________                                        Temperature, °C.                                                                    Soaking time required, seconds                                   ______________________________________                                         89          35                                                                95          50                                                               100          35                                                               105          60                                                               ______________________________________                                    

The variation in the time required for full impregnation illustrates thedifficulty of reproducibly manufacturing a product of prime quality. Inthis case also, the product surface became smeary.

EXAMPLE 4

In these experiments pulped broke of different qualities intended forthe production of beer glass pads was used. The grammage of the materialvaried from 540 to 775 g/m² and the thickness varied from 1.4 to 2.2 mm.Impregnation was slow for all the tested qualities. Some of the productswere very smeary, whereas others were much less so. None was acceptablein this respect, however. The longest burning time was obtained with"unbleached beer glass pad board", 2.2 mm thick and with a grammage of775 g/m² : 4.5 minutes. Impregnation was poor with unbleached, sized"beer glass pad board", and hence the burning time was shorter, 3.5minutes, although the grammage was the same.

EXAMPLE 5

In this example, which is according to the invention, the pulp consistedof a mixture of so called CTMP, ie thermomechanical pulp, chemicallymodified by a solution of sodium sulphite/bisulphite, and sulphate pulp.The raw material for the pulp was pine tree wood chips, a mixture ofNordic fir (Picea albis) and pine (Pinus silvestris). The grammage was625 g/m² and the thickness 2.3 mm. The soaking with paraffin wascompleted in but 8 seconds at a temperature of 105° C. Excess paraffindrained quickly in the draining zone. The finished lighting aid wascompletely dry on the surface, i e it did not smear, and had a fibroustexture to the touch, as is desirable. It was easily packed and labeled.The burning time was appr 6.5 minutes.

We claim:
 1. A method of producing an ignescent material, said methodcomprising feeding cellulose pulp in the form of an elongate web havinga thickness of between 1 and 4 mm and a grammage of between 550 and 700g/m² through a bath of molten, combustible, organic impregnatingsubstance consisting essentially of paraffin having a melting point ofbetween 50° and 60° C., to thereby impregnate said pulp with saidimpregnating substance, at least 75% of said pulp being chemicallymodified thermomechanical pulp (CTMP) with the balance being essentiallysulphate pulp, said impregnating substance being at an impregnation melttemperature of over 90° C. during impregnation of said web.
 2. Themethod according to claim 1, wherein said web has a thickness of between1.5 and 3 mm, and a grammage of between 550 and 700 g/m².
 3. The methodaccording to claim 1, wherein said impregnation melt temperature isabove 100° C. and not above 130° C.
 4. The method according to claim 3,wherein said impregnation melt temperature is above 100° C. and notabove 115° C.
 5. The method according to claim 3, wherein saidimpregnating substance is paraffin having a content of oils andaromatics not greater than 1%.
 6. The method according to claim 5,wherein said content of oils and aromatics is not greater than 0.5%. 7.The method according to claim 3, wherein said web has a dwell time insaid melt of 5 to 20 seconds.
 8. The method according to claim 7,wherein said dwell time is not more than 15 seconds.
 9. The methodaccording to claim 1, wherein excess impregnating substance is allowedto drain off said web, said web thereafter being cooled at a temperatureof between 20° C. and 40° C. while kept flat, said web being finally cutinto flat sheets having a thickness essentially the same as that of theweb prior to impregnation.
 10. The method according to claim 9, whereinsaid web is cooled at a temperature of between 25° and 35° C.